Insulating washer for brush-holder bracket arms



` 1,632,096 JUN 14 1927' R. H; NEwrcN NSULATING WASHER FOR BRUSH HOLDER BRACKET ARMS Filed Sept. 26, 1925 wl EssE lNvNToR d Y BY @L d ATTORNEY members Patented June 14, 1927.

REX' H. 1\TE\'1O1\T'OEYVl/'ILKINSBU'RGr,l PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC '& MNUFACTURNG COMPANY, A CORPSRATON OF PENNSYLVANIA..

INSULATING WASHER-FOR'BRUSHLHOLDER/BRACKET' ARMS Application filedSeptembcr 2G, 1925.

My presentinvention relates to improvements in supporting means for brush-holder brackettarms, such. as are utilized in dynamo-electric machines. Y

It has been `the usualpracticeto mount thebrush-holder br( cket .arms on an insulatingY ring extendingfaround they entire eircumference, in'space'd yrelation to the commutator or slip ring with which the brushes yco-operate. ln certain instances, the use of an insulating` ring has been avoided by mounting the brush-holder bracket arms directly upon a metallic portion of the stator frame and insulated therefrom by means of large, flat insulating washers back of the bracket arms.

The utilization of an insulating supporting ring is objectionable on account of its higher cost, and its susceptibility to breakage, resulting in frequent delays in repairing, which are brought about vby the necessity for disconnecting all of the bracket arms when a new insulating supporting ring is inserted.v rllhe utilization of the secondinentioned construction, having large, flat insulating washers, is subject to the disadvantage that the dirt-laden air, blown around .by the rotating current-collecting device, soon deposits a lilm of oily conducting particles covering all exposed surfaces and eventually resulting in a llashover between a brush-holder supporting arm and the metallic frame member, the arc discharging across thesurface of the flat insulating washers.

The object of the present invention is to avoid the disadvantages of the prior constructions just mentioned, by the utilization of cupped insulating washers having flange port-ions extending outwardly from the metallic supporting member of the stator frame. My new construction is cheaper than the, large circumferential insulating heretofore used. Moreover, it provides insulation which is superior to that obtained either with the insulating supporting ring or with the large, fiat insulating washers of the prior art, since the out-- wardly-disposed flanges of my cup-shaped insulating Washers provide an increased creepage surface which is e'ective on both sides of the insulating 1nember.

That is, if the windage of the machine causes the sides of the insulator flanges. which are exposed to the clockwise rotational Serial No.y 58,8 13.

aircurrents, to become coatedwith oil, .the other surface of the outwardly-extending flanges willstill be available for furnishing he necessary protection. ln this way, a much better result can be obtained and, in the case of diiliculty, replacement is easy and inexpensive.

It hasbeen found, also, that the material of which my improved washer is made has a very definite bearingv on. itsefliciency.- f smooth surface, to prevent dirt-accumulation, and a material that will not become carbonized, are both essential characteristics of such washers. In the accompanying drawing,

Figure l is a perspective view showing the direct-current side of a rotary converter embodying my invention, and

Fig. 2 is a perspective view of one of the insulating washers det-ached.

As shown in Fig. 1, the current-collecting device l is engaged by a plurality of brushes 2 which are supported by individual supporting arms or brackets 3 of conducting material. The brush-holder bracket arms 3 are carried by, and insulated from, a metallic ring el which is a part of the stator frame lisposed between the bracketsupporting frame-portions 4l and each bracket arm 3 is one of my improved dished insulating washers 7, which is illustrated more clearly in Fig. 2.

he insulating washer comprises a base portion 8 surrounded, on all four sides, by flanges or outwardly-extending portions 9, whereby the creepage distance is increased. by causing the creepage to occur on both sides of the flanges, whereas, in the flat washer construction, the creepage is only over the outer or exposed surface of the portion of the washer which projects beyond the base of the bracket arm. Also, in the use of my invention, the creepage resistance is greatly increased by reason of the fact that, regardless of the direct-ion of rotation, at least one of the surfaces of the outwardly-extending flanges will be protected from exposure to the blast of dirt-laden air which is carried around by the rotating current-collecting device, and hence, one clean insulator surface is always available to interrupt any possible creepage path.

My novel insulating washer herein described has been thoroughly tested in actual practice and has been found to be a very remarkable improvement upon all types of insulating mountings for the brush-holder supporting arms of large, high-voltage macliines.

I claim as my invention:

l. The combination with a rotating current-collecting device, a co-operating brush, a brush-holder for said brush and a bracket arm of conducting material for supporting said brush-holder, of a conducting frame member to which said bracket arm is insulatingly attached, and means for preventing the formation of a continuous film of oily conducting material joining said frame member and said bracket arm, said means comprising a dished insulating washer disposed between said bracket arm and said frame-member and having ianges extending outwardly away from said framemember across the direction of flow of the from said supporting member for providin an insulating surface, which is protect from the windage of the rotating device, in the leakage path from each bracket.

In testimony whereof, I have hereunto subscribed my name this 20th day of August, 1925.

REX H. NEWTON. 

